Safety-valve



(No Model.)

T. H. SYMINGTON.

SAFETY VALVE.

No. 581,790. PatentedvMay 4,1897.

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WKTNESSES'.

llNTTnn STATns PATnNT @Tricia THOMAS HARRISON SYMINGTON, OF RICHMOND,VIRGINIA.

SAFETY-VALVE.

SPECIFICATION forming part of Letters Patent No. 58 1 ,7' 90, dated May4c, 1897.

Application iiled September Z, 1896. Serial No. 604,629. (No model.)

T0 all whom, t may concern:

Be it known that I, THOMAS HARRISON SY- .WIINGTON, a citizen of theUnited States, and a resident of Richmond, in the county of I'Ienricoand State of Virginia, have invented certain new and useful Improvementsin Safety- Valves, of which the following is a specification.

The object of my invention is primarily to secure a prompt andsufficient openin g for the escape of steam from a closed vessel whenthe pressure rises to a very few pounds above the maximum allowed for,and also to provide means for preventing the formation of a vaeuum inthe said vessel.

The ordinary form of valve held shut against pressure by a spring opensslightly when the force of the spring is overcome by pressure, but toget a large opening to take care of a large volume of steam the pressuremust rise very much above the pressure necessary to overcome theresistance of the spring, because as the spring is compressed itsresistance increases, and the valve can therefore only be opened wide bya large increase of pressure.

My invention consists of a valve intended to be used on the steam-chestconnected with the low-pressure cylinder of a locomotive for preventingany undue pressure in said chest, and also to prevent the formation of avacuum therein when the engine is running without steam. This valve isconstructed in such a way as to open automatically when the throttle isclosed and stay open while the engine is running under this condition,and also to close instantly and stay closed as soon as the throttle isopened. It is also constructed to open when the pressure in thesteam-chest exceeds a certain value. In other words, this valve servesthe double function of preventing an excessively-low andexcessively-high pressure in the steam-chest and cylinder.

The following is a specification of the construction and operation ofthis valve, reference beinghad to the accompanying drawings.

Figure 1 is a vertical sectional view of the valve, and Fig. 2 a planview taken on line oc of Fig. 1.

Referring to Fig. 1, 2 is the valve-casing, having a portion 1 threadedon the outside to admit of 'the valve being screwed into thesteam-chest. The threaded portion is not shown in the drawings.

19 is a cap for closing the top of the casing, and 2O a cap for closingthe bottom. The lower cap 20 contains a recess 22, in which slides thevalve-stem S.

7 is thevalve. The chamber 3 is in direct communication with the steamchest, and when the valve falls away from its seat ll, 3 is connectedwith the atmosphere through the chamber a and holes 12.

17 is a valve held to its seat by means of the spring 1S, which shouldbe set to open at the desired pressure. The cap 2l closes thevalve-chamber G.

2st are packing-rings, and 23 a hole through the valve-casing throughwhich any steam which has leaked past the packing-rings may escape.

13 is a piston working in the cylinder 5.

1l is a piston-rod connected thereto.

15 is a diaphragm separating chamber J. from chamber 5 and having acentral perforation through which passes the piston-rod 14.

15 is a boss on the under side of the diaphragm around its centralperforation, which serves as a guide for the piston-rod.

The piston -rod 14 projects through the chamber et and into a recess inthe center of the valve 7.

10 10 are holes bored through the base of the valvesocket 9, so as toestablish a connection between the steam-space 3 and the space 22 belowthe valve-stem. This space is provided in order to have an excess ofarea on the lower surface of the valve 7 exposed to steam-pressuresufficient to return it to its seat against pressure exerted upon itsupper surface.

The combined area of the under surface of the valve 7 and that part ofit which projects into the space 22 is, however, less than the area ofthe piston 13.

In operation the action of the valve is as follows: Under ordinaryconditions, with the throttle open, the valve 7 is held up against itsseat by steam-pressure on its lower surface. If, however, due to theengine being suddenly reversed or other causes, the pressure in thesteam-chest should rise above a certain value, the valve 17 would bepushed up, steam admitted through opening 1G and IOO by Way of port 23to the upper side of piston 13, and since the area of piston 13 isgreater than the area of valve 7 on its lower side the said Valve wouldbe pushed down away from its seat by the rod 14, thus opening a largepassage for the escape of steam from the chamber 3 into chamber 4 and tothe atmosphere through holes 12. As soon as the pressure is sufficientlyreduced by the escape of steam to the atmosphere the spring 1S pressesthe valve 17 back to its seat and shuts off the steam from piston 13 andthe pressure on the under surface of the valve 7 returns it to its seat,and communication with the atmosphere is closed.

If the throttle is closed and the engine run Without steam, all pressurewill be removed from the under surface of the valve 7 which will fallaway from its seat by gravity and allow free access of air intosteam-chest by holes 12 and chambers l and 3,- thus preventing theformation of a vacuum in the steam chest and cylinder. As soon as thethrottle is again opened and steam admitted into` chambers 3 and 22 thevalve 7 will be returned to its seat immediately and communication Wit-hthe atmosphere cut off.

What I claim, and desire to secure by Letters Patent, is-

1. In a relief-valve, the combination of a main valve closing apressure-chamber and opening to exhaust a cylinder and piston thereinwith means connecting the piston with the main valve to open it, asupply-port connecting the pressure-chamber with the cylinder, aspring-actuated pressure-valve closing said port, and an opening underthe mainvalve stem for the purpose of admitting steam and raising thesaid valve, substantially as described.

2. In a relief-valve the combination of a main valve closing apressure-chamber and opening to exhaust, With a cylinder and pistontherein, a piston-rod actuated by said piston and bearing upon the mainvalve to open it, a steam-port connecting the cylinder with thepressure-chamber, a pressure-valve closing said port, and an openingunder the main-valve stem for the purpose of admitting steam and raisingthe said valve, substantially as described.

3. In a relief-valve, the combination of a pressurechamber, connectedwith steampressure, an exhaust-chamber connected by large apertures tothe atmosphere, a cylinder, a piston in said cylinder, a steam-portconnecting the pressure-chamber with the cylinder and closed by thepressure-valve, a main valve closing the communication between thepressure-chamber and exhaustchamber and opened by the mot-ion of thepiston in the cylinder, and an opening under the main-valve stem for thepurpose of adm-itting steam and raising the said valve, substantially asdescribed.

4l. In a relief-valve the combination of a pressure-chamber, anexhaust-chamber provided with large peripheral perforations, a mainvalve separating these chambers, a means for opening the valve againstpressure, a means for opening it toV prevent the formation of a vacuumin the pressure-chamber, and means for closing the said valve when steamis again admitted to the pressurechamber, substantially as described.

5. In a relief-valve the combination of a pressure-chamber and anexhaust-chamber, the exhaust-chamber having large peripheral openings, amain valve separating the chambers, a cylinder and piston therein, andpiston-rod, passing through the piston and bearing upon the main valve,the area of the piston being larger than the valve, a port admittingsteam from the pressure-chamber to the cylinder, a pressure-valveclosing said port, and an opening under the main-valve stem for thepurpose of admitting steam and raising the said valve, substantially asdescribed.

Signed at Baltimore, in the State of Maryland, this 20th day of May, A.D. 1896.

THOMAS HARRISON SYMINGTON.

"Witnesses:

J. HENRY STROHMEYER, M. G. STEUART.

